Automotive fuel supply apparatus and control valve

ABSTRACT

A fuel delivery arrangement for a fuel injected engine 12 has a single fuel line 16 extending from an in-tank fuel pump 14 to a fuel rail 18. Included within the fuel line 16 is a check valve 24 which allows fuel flow from the tank to the fuel rail but which prevents return flow while allowing any trapped fuel between the fuel rail and the check valve to expand to reduce pressure.

FIELD OF THE INVENTION

This invention relates to a fuel supply arrangement for use with anautomotive engine which has a fuel injection system. More specifically,this invention relates to a pressure control valve for maintaining anacceptable pressure to a fuel injection system.

BACKGROUND OF THE INVENTION

In fuel injected engines, it is essential to ensure that the pressure offuel delivered to the injectors is accurately controlled so that eachtime an injector opens the desired quantity of fuel is forced throughthe injector nozzles into the cylinders of the engine.

In order to ensure that the correct fuel pressure is obtained, it isconventional to supply the injectors with fuel from a fuel rail, and forthe fuel rail to be connected to the fuel tank through feed and returnpassages. The fuel pump operates continuously, at a constant rate andpumps more fuel per unit time to the rail than is required. The excessfuel is returned to the tank through the return line. A pressureregulator is conventionally incorporated in or near the fuel rail.

Proposals have been made to operate fuel injection systems with only onefuel pipe leading between the fuel tank and the fuel injectors at theengine. Such systems are conventionally known as `returnless` fuelsystems. The fuel pump in such a system will operate in accordance withengine demand and under certain conditions (e.g., deceleration) willstop running and the injectors will be closed. It is important then thatthe correct fuel system operating pressure is maintained at theinjectors so that when demand returns and the injectors are operated,fuel at the correct pressure is present at the injectors.

In order to maintain this pressure, a check valve can be provided in thefuel line, as described in U.S. Pat. No. 4,964,391. However the volumeof fuel trapped between the check valve and the injectors can be subjectto external influences, for example temperature changes, which willalter the pressure under which the trapped volume is held. Such changesare undesirable.

SUMMARY OF THE INVENTION

According to the present invention there is provided a fuel deliveryarrangement for an internal combustion engine, the arrangementcomprising a fuel reservoir, a pump, a fuel line along which fuel fromthe reservoir is pumped to the engine and a check valve in the fuelline, the check valve having a valve member movable relative to a valvebody to open and close a valve opening, the valve being arranged to opento permit fuel flow to the engine when the pressure on the reservoirside of the valve is greater than the pressure on the engine side and toclose when the pressure differential is reversed, and wherein the valvemember is able to continue to move after having closed the valve openingin order to maintain the pressure of the fuel volume enclosed betweenthe valve member and the engine.

The ability of the valve member to continue to move after closing theflow passage allows pressure variations (in both directions) to beaccommodated in the volume of fuel trapped between the valve and theengine, so that the pressure behind the injectors remains within adesired range.

The valve member may be in the form of a piston travelling in acylindrical chamber with one of the fuel line connections to the chamberintermediate the ends of the chamber so that the valve member closescommunication between the connections before it reaches the end of itstravel in the chamber. The valve member can include a nonreturn valveoperating in a direction opposite to that of the check valve and adaptedto open at a pressure substantially higher than the opening pressure ofthe check valve.

Alternatively, the valve member may comprise a closure member supportedon a diaphragm, with the diaphragm being free to distend after theclosure member has closed on a valve seat, in order to increase thevolume enclosed between the valve member and the engine.

The arrangement may comprise only a single fuel line between the engineand the fuel tank, in which line the check valve is fitted, and meansfor controlling the operation of the pump in accordance with engineoperating parameters such as throttle pedal position, fuel temperatureor intake manifold vacuum.

According to another aspect of the invention, there is provided a fueldelivery arrangement for an internal combustion engine, the arrangementcomprising a fuel reservoir, a fuel pump, a fuel line along which fuelfrom the reservoir is pumped to the engine, a check valve in the fuelline, the check valve having a valve member movable relative to a valvebody to open and close a valve opening, and means for controllingoperation of the pump to vary the delivery of the pump in dependence onengine operating parameters, wherein the check valve is arranged to opento permit fuel flow to the engine when the pressure on the reservoirside of the valve is greater than the pressure on the engine side and toclose when the pressure differential is reversed, and wherein the valvemember is able to continue to move after having closed the valve openingin order to maintain the pressure of the fuel volume enclosed betweenthe valve member and the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a fuel delivery arrangement in accordancewith the invention.

FIG. 2 shows the control valve in a closed position which does not allowflow through the valve or further expansion of the valve member to takeup excess pressure.

FIG. 3 shows the control valve member in the normal fuel supplyposition.

FIG. 4 shows the control valve member in a position after pressuregenerated by the fuel pump at the control valve inlet drops relative topressure at the control valve outlet.

FIG. 5 is a cross-section through a second embodiment of the valve inaccordance with the invention.

FIG. 6 is a cross- section of a practical embodiment of a check valve inaccordance with the present invention which works on the same principleas the valve shown in FIGS. 2, 3 and 4, and is shown in the sameposition as that in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a schematic arrangement in which fuel is delivered from afuel tank 10 to an engine 12. A pump 14 is housed within tank 10 anddraws fuel from tank to pass it along a fuel line 16 leading to a fuelrail 18. From fuel rail 18, fuel is injected into the cylinders of theengine (four cylinders in the scheme shown in FIG. 1) through respectiveinjectors 20. The arrangement includes a pressure transducer 22 whichsenses the pressure in the line 16 and passes a signal to an electronicpump speed control module 23 which controls the operation of pump 14,and a check valve 24. Valve 24 can be fitted at various positions inline 16. In FIG. 1, valve 24 is shown at a position just downstream ofpump 14, but other positions are possible. For example, valve 24 couldbe fitted within the housing of pump 14, or it could be fitted closer tothe engine. The preferred position is, however, in close associationwith tank 10.

It is important to ensure that the pressure maintained within fuel rail18 is maintained within the desired limits whatever the speed of theengine. As the engine speed varies, so will the rate of fuel consumptionand consequently also the rate of delivery from pump 14.

During normal operation, valve 24 will be opened by the fuel pressuregenerated by pump 14 to allow flow to fuel rail 18 in the directionindicated by the arrow 26. There will however be occasions when thepressure in fuel rail 18 is above the desired level, for example whenthe engine speed suddenly drops if the driver takes his foot off theaccelerator. In such a case, it will become necessary to relieve thepressure, and check valve 24 is constructed in order to allow this tohappen.

FIGS. 2, 3 and 4 show check valve 24 positioned in fuel line 16 with afuel inlet 16a and an outlet 16b. A valve chamber 30 contains a linearlymoveable valve member 32 which is urged towards the left hand end ofchamber 30 by a return spring 34. A fuel branch passage 36 is providedbetween outlet 16b and chamber 30.

In use, when pump 14 starts to operate, pressure will build up in checkvalve inlet 16a, and this will cause valve member 32 to move to theright to the position shown in FIG. 3 where communication is openedbetween inlet 16a and outlet 16b. This is the normal fuel supplyposition. The pressure of the incoming fuel 16a will be working againstthe restoring force of the spring 34 and against the pressure exerted onthe back of the valve member through the branch passage 36. While fuelis being supplied to fuel rail 18, valve 24 will remain in the positionshown in FIG. 3.

However if the pressure generated by pump 14 in fuel line 18 drops sothat the pressure at inlet 16a drops relative to the pressure of outlet16b, then valve member 32 will move to the left to the position shown inFIG. 4, where it obscures outlet 16b and prevents fuel from fuel rail 18from flowing in the opposite direction, back to tank 10. When thishappens there is a trapped volume of fuel within fuel rail 18 and theupstream part of fuel line 16, which is in communication with valvemember 32 through branch passage 36. The pressure under which thistrapped volume is maintained may be greater than desired and, if this isthe case, then the fluid pressure acting through passage 36 can berelieved by a further movement of valve member 32 to the left, and thesize of chamber 30 is designed to allow this. The further movement ofvalve member 32 to the left beyond the position shown in FIG. 4 to theposition shown in FIG. 2 will increase the volume occupied by thetrapped fuel, and will thus reduce the pressure under which this trappedfuel is maintained. The valve member can therefore shuttle between itsFIG. 2 and FIG. 4 positions to control the pressure of the trapped fuelbehind valve member 32. The cross-section of branch passage 36 will berelatively small to allow flow through it.

The embodiment shown in FIGS. 2, 3 and 4 also includes an additionalone-way valve consisting of a spring-loaded ball 38 which normallycloses a narrow passage 40. Under most conditions this valve will remainclosed but if an exceptionally high pressure should occur in fuel rail18 and in fuel line outlet 16b and in branch passage 36, then ball 38can lift off its seat to open passage 40 and to relieve this pressure.

FIG. 5 shows an alternative embodiment where a check valve 124 has ahousing with a fuel inlet 116a and a fuel outlet 116b. A valve member132 is mounted at the center of a flexible diaphragm 133, and in theclosed position shown in FIG. 5 the valve member 132 is pressed by areturn spring 134 against a seating member 135 so that a hole 137 in thecenter of the valve member is closed. In this position there is no flowthrough the valve. However if the pressure at the inlet 116a rises, thenthe pressure acting on diaphragm 133 and on valve member 132 willovercome the pressure of spring 134 and valve member 132 will lift offseat 135 to allow flow through valve 124. Diaphragm 133 will take upposition 133b under this condition. When, subsequently, the pressure atoutlet 116b rises above that of inlet 116a, then valve member 132 willbe pressed against valve seat 135 to close passage 137. If the pressurein outlet 116b is still above that of inlet 116a, then this pressure canbe relieved by distention of diaphragm 133 which will change shape sothat it takes up the position indicated in dotted lines at 133a. Theresulting increase in volume on the right hand side of the diaphragmwill relieve the pressure in fuel rail 18.

The embodiment shown in FIG. 5 does not include a one-way valvecorresponding to valve 38, 40 in FIGS. 2, 3 and 4, but such a valve canbe provided separately between check valve outlet 116b and fuel rail 18.

FIG. 6 shows a check valve 224 which is a practical embodiment of avalve working on the same principle as the valve shown in FIGS. 2, 3 and4. The valve has a housing made up of two parts 242 and 244, with thesetwo parts being threaded together at 246. Valve 224 has an inlet 216a,an outlet 216b, a piston-like valve member 232 and a return spring 234.In the position shown in FIG. 6 (which corresponds to the position shownin FIG. 2) valve member 232 is in its left hand end position and sitsagainst an O-ring 248 to close inlet 216a.

When the pressure in inlet 216a rises, valve member 232 is pushed to theright against the restoring force of spring 234. When valve member 232is moved far enough to allow the fuel from inlet 216a to flow into land250, then fuel will begin to flow from land 250 along axial grooves 252,into space 254 behind valve member 232 and out of valve 224 throughoutlet 216b.

If the pressure in inlet 216a drops and that in outlet 216b remainshigh, valve member 232 will move to the left to close communicationbetween land 250 and inlet 216a. If there is a greater pressure atoutlet 216b than at inlet 216a, then valve member 232 will move furtherto the left to allow the fuel in outlet 216b more space.

The nonreturn valve 38, 40 shown in FIGS. 2, 3 and 4 can be providedwithin valve member 232 or independently.

The check valve described thus allows a fuel injection system to be fedwith fuel through a single fuel line 16 and through a single valve 24.The permissable movement of the valve member 32, 133, 232, beyond the"valve closed" position allows sufficient additional volume to beoccupied by the trapped fuel to reduce the pressure of this fuel towithin the desired limits.

Although the preferred embodiment of the present invention has beendisclosed, various changes and modifications may be made withoutdeparting from the scope of the invention as set forth in the appendedclaims.

I claim:
 1. A fuel delivery apparatus for an internal combustion engine,said apparatus comprising:a fuel reservoir; a pump; a fuel line alongwhich fuel from said reservoir is pumped by said pump to said engine;and a check valve in said fuel line, comprising a valve body having apiston able to travel relative thereto in a cylindrical chamber formedtherein to open and close a valve opening located intermediate betweenends of said chamber so that a first end of said piston closes saidvalve before reaching an end of travel in said chamber, said check valvehaving an inlet in communication with said reservoir and said pumpthrough said fuel line, and an outlet in communication with said enginethrough said fuel line, said valve being arranged to open to permit fuelflow to said engine when pressure in said inlet of said valve is greaterthan pressure in said outlet, and to close when the pressuredifferential is reversed, and wherein said said valve member is able tocontinue to move after having closed said valve opening in order tomaintain the pressure of a fuel volume enclosed by a second end of saidpiston and an end of said chamber.
 2. An apparatus according to claim 1wherein said outlet of said valve has a reverse flow branch passageleading from said outlet to a valve chamber behind said valve member,said branch passage allowing fuel to enter said valve chamber to exert apressure on said valve member.
 3. An apparatus according to claim 2wherein said branch passage has a flow cross-section smaller than theflow cross-section of said outlet.
 4. An apparatus according to claim 1wherein said piston includes a non-return valve operating in a directionopposite to that of said valve and adapted to open at a pressuresubstantially higher than an opening pressure of said valve.
 5. Anapparatus according claim 1 wherein said valve member comprises aclosure member supported on a diaphragm, said diaphragm being free todistend after said closure member has closed on a valve seat, in orderto maintain the pressure of a fuel volume enclosed between said valvemember and said engine.
 6. An apparatus according claim 1 comprising asingle fuel line between said engine and said fuel tank, in which linesaid valve is fitted, and means for controlling operation of said pumpin accordance with engine operating parameters such as throttle pedalposition, fuel temperature or intake manifold vacuum.
 7. A fuel deliveryapparatus for an internal combustion engine, said apparatus comprising:afuel reservoir; a pump; a fuel line along which fuel from said reservoiris pumped by said pump to said engine; and a check valve in said fuelline, comprising a valve body having a piston able to travel relativethereto in a cylindrical chamber formed therein to open and close avalve opening located intermediate between ends of said chamber so thatsaid piston closes said valve before reaching an end of travel in saidchamber, said check valve having an inlet in communication with saidreservoir and said pump through said fuel line, and an outlet incommunication with said engine through said fuel line, said valve beingarranged to open to permit fuel flow to said engine when pressure insaid inlet of said valve is greater than pressure in said outlet, and toclose when the pressure differential is reversed, and wherein said saidvalve member is able to continue to move after having closed said valveopening in order to maintain the pressure of the fuel volume enclosedbetween said valve member and said engine, said valve member also havinga non-return valve operating in a direction opposite to that of saidcheck valve and adapted to open at a pressure substantially higher thanan opening pressure of said valve.